Optical Coherence Tomography (OCT) is used in the ophthalmic industry in pachymetry, anterior chamber depth, axial length, and retinal imaging applications. Known OCT systems typically use either a time domain or a spectral domain technology to provide line of sight length optical analogs of the echoes in ultrasonic imaging via homodyne detection. With the use of broadband sources, there is homodyne signal amplitude when the reference and signal beams are sufficiently close in optical delay. Time domain and spectral domain OCT use collinear reference and signal beams to achieve a detectable interference that includes the depth information.
Currently known OCT systems involving axial measurements may be negatively impacted by axial or transverse eye movement during the measurement. For example, existing time domain measurements techniques used to measure axial length may be prone to such errors where a mirror must be physically scanned to scan the depth range. Relatedly, many currently known spectral domain methods typically do not afford the depth of range desirable for axial length measurements because the depth range is determined by the spectral resolution of the spectrometer/detector combination. In many instances, the range which may be obtained from such instruments is effectively limited to a maximum of about 5 mm. In addition, existing spectral domain OCT techniques may be prone to ghost images.
Some have proposed multiple spectral domain OCT systems with offset axial depth locations, single or multiple SLD sources for use with separate spectrometers for each depth, and the implementation of switchable time delay references (e.g., using fiber switches with different length fibers) for spectral domain OCT to address these limitations. However, many time such proposals suffer from high costs.
Hence, although current techniques may provide real benefits to those in need, still further improvements may be desirable. Embodiments of the present invention provide solutions to at least some of these outstanding needs.